As wireless telephones and other communications devices become increasingly powerful, a need arises to transfer information to and from such devices at faster rates. At present, many portable wireless devices contain sufficient computing power to process digital music, video and/or other media services, yet challenges remain in delivering sufficient bandwidth for such services to the device. Conventional global service mode (GSM) phones, for example, are currently limited to about 114 kbps of data throughput using the general packet radio service (GPRS) standard. While this is sufficient for general web browsing and many other applications, many consumers have expressed a desire for faster data rates.
Transmission standards for wireless data and services continue to evolve and to provide increasing throughput for emerging features and capabilities. An example of a standard that promises additional bandwidth is the “Enhanced Data Rate for GSM Evolution” (EDGE) standard, which promises data rates up to 384 kbps. Further, EDGE implementations typically make use of conventional GSM timing and signaling frames, thereby making their adoption relatively straightforward for the service provider. Frequently, emerging communications standards provide additional bandwidth by modulating transmitted signals in a manner that allows existing mechanisms to transmit additional data. The EDGE standard, for example, uses a polar modulation scheme to represent multiple data bits with conventional GPRS symbology. The addition of polar modulation therefore allows for greatly increased bandwidth, without requiring significant reworking of the underlying communications architecture.
With regard to particular telephone handsets, however, the added technical demands levied by the faster data rates can present various engineering challenges. In particular, it can be relatively difficult to control the power amplifier (PA) of the device in a manner that both precisely applies the polar modulation schemes used by EDGE and other protocols while still making efficient use of electric power supplied by the battery. Various “open loop” and “closed loop” control schemes have been developed, yet results have been varied to date. Many so-called “open loop” control schemes, for example, lack the capability to efficiently drive the power amplifier, or to respond to environmental changes such as changes in temperature. So-called “closed loop” control schemes, while effective operating the device PA, can be complicated and expensive to implement, and can themselves draw significant amounts of battery current, thereby further reducing the efficiency of such implementations.
Accordingly, it is desirable to implement systems and techniques for controlling the power amplifier of a wireless device in a manner that is effective, yet efficient. More particularly, there is a need to implement a polar modulation scheme in a power amplifier in a manner that makes efficient use of battery power, chip space and other resources. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.